An electrical machine generates heat in its various parts because of mechanical losses, magnetic losses and electrical losses. This excess heat has to be removed. The heat is often transferred to a cooling fluid which is circulated in the electrical machine and then cooled in a separate cooling unit after which it is returned back to the electrical machine.
In applications like wind turbine generator systems the space is precious. A wind turbine nacelle has compact dimensions and place requirements on the size of the cooling unit and its heat exchangers.
A heat exchanger for cooling an electrical machine is typically installed on the top of the electrical machine increasing the total height of the wind turbine generator. The cooling fluid circulation of the electrical machine needs often also fans or pumps to enhance the cooling fluid circulation in the heat exchanger. These fans or pumps also increase the required free height in the nacelle.
The drawback with the previous solutions in a heat exchanger for the electrical machine is its requirements for the space and the free height.